Numerous systems have been developed for correcting errors in legible matter which may have been applied to a substrate, especially a paper, by typewriting, hand writing, drawing or some other method of applying legible matter to a substrate.
For example, in office use, white-pigmented dispersions containing a volatile organic solvent may be used to correct typewriting or the like by applying the dispersion with a brush. Upon evaporation of the highly volatile organic solvent, an opaque cover layer is formed which renders the underlying legible matter substantially invisible.
However, the solvents used constitute an environmental hazard upon evaporation and it is generally difficult to apply the dispersion with the brush in a fully uniform manner. In addition, one must wait a relatively long time before evaporation is complete and the correction can be overtyped. Mention may also be made of a correcting method in which legible matter is covered by an adhesive strip which is applied to the substrate and consists of a strip of white paper which has the same color as the substrate and is bonded to the latter over the line of legible matter. The paper strip is relatively thick so that truly invisible corrections cannot be made in this fashion. Incidentally, it is not uncommon for the adhesive layer of such strips to be provided with a masking strip which must be pulled away to expose the adhesive layer before the latter is applied to the substrate. Neither approach has been found to be fully satisfactory.